President Thabo Mbeki of South Africa said yesterday that the government and opposition in Zimbabwe were to negotiate a solution to their their country's crisis.

He said President Robert Mugabe and the Movement for Democratic Change had agreed to begin formal talks to end the political repression and economic collapse which has made the regime an international pariah.

At a joint news conference in Pretoria with the German chancellor, Gerhard Schröder, Mr Mbeki staked his credibility on the talks.

"I'm happy to say that they have agreed now that they will go into formal negotiations. I'm saying that I'm quite certain that they will negotiate and reach an agreement."

If confirmed, the negotiations could mark the beginning of the end of Zimbabwe's nightmare. But both sides said yesterday that they were unaware of the the political deadlock being broken, prompting the suspicion that Mr Mbeki had hyped up informal "talks about talks".

Mr Mbeki is under heavy pressure at home and abroad to show that his softness towards Mr Mugabe, whose authoritarian rule has destabilised southern Africa, is yielding dividends.

During a break in his trial for treason the MDC leader, Morgan Tsvangirai, denied knowledge of a breakthrough.

His spokesman, William Bango, said there was no sign of movement.

"We are still waiting to hear from Zanu-PF on the way forward," he said, adding that the last meaningful contact had been in September, when Zimbabwean bishops acted as intermediaries between Mr Tsvangirai and Mr Mugabe.

There was no official response from the government. The justice minister, Patrick Chinamasa, who has led Zanu-PF's informal talks, said: "I am on leave and I am not aware of any new developments in this regard."

Several times in the past 12 months Mr Mbeki has assured western leaders, including President George Bush, of behind-the-scenes progress in Harare which would lead to a resolution by June.

But the security forces and government supporters have continued to beat and jail opponents and the economy has continued to slide, making millions dependent on international food aid.

Analysts suggest that Mr Mbeki's statement may have been prompted by a private promise by Mr Mugabe to improve his image before the European Union takes a decision next month whether to renew sanctions on leading members of Zanu-PF.